A new nanoparticle, created at the University of California and tested on live animals can illuminate cancerous tissues and biodegrades with no lasting detrimental effects. (Source: Luo Gu)

A University of California researcher examines the new nanoparticles. The particles are created from flakes of silicon, which are special treated to glow red when UV light is shined on them. (Source: Luo Gu)

The silicon nanoflakes, shown here up-close, were also shown to be able to slowly release a chemotherapy drug specifically to target cancer cells. (Source: Luo Gu)

Unlike many new nanomedicine studies, a new one bears toxicity of nanoparticles in mind

Nanoparticles are an incredibly promising treatment option when it comes to many life-threatening diseases such as cancer. The small size and often organic composition of nanoparticles allows them to bind and enter cells, delivering drugs or marking diseased tissues. However, a serious downside of nanoparticles is that many have been initially shown be quite toxic, possibly being more dangerous than asbestos to the human body.

At the University of California, San Diego, they're well aware of the toxicity dangers of nanotechnology, so they designed their latest cancer fighting particle with safety in mind. Michael Sailor, a chemistry professor at the university and leader of the study describes, "It is the first luminescent nanoparticle that was purposely designed to minimize toxic side effects. This new design meets a growing need for non-toxic alternatives that have a chance to make it into the clinic to treat human patients."

Professor Sailor's lab tested numerous luminescent nanoparticles, only to find that many of them were far too toxic for injection into humans. Typically, glowing nanoparticles use toxic organic chemicals or tiny structures called quantum dots, which can leave potentially harmful heavy metals.

The researchers ditched these toxic alternatives and used silicon nanoflakes to do the job. Silicon wafers were made porous by applying an electric current and were then smashed into tiny pieces by ultrasound. The resulting flakes were then treated to make them glow red when exposed to ultraviolet light.

The new nanoparticles were shown to be biodegradable and did not harm mouse test subjects. Attaching markers for known tumors, the nanoparticles attached to tumors in the mice and glowed red. After several hours, the glow disappeared and after several weeks the nanoparticles were entirely flushed out of the system with no known side effects. The test was the first example of tumors and organs being imaged using biodegradable silicon nanoparticles in live animals.

The new particles could soon be employed in human medicine to detect tiny tumors. They could also be used to verify that surgery on tumors was a complete success. Furthermore, they could be altered to deliver drugs safely and with specificity to cancer cells. The drug doxorubicin was shown to bind to the nanoparticle and be slowly released as it dissolves. This form of delivery could almost completely eliminate the side effects of chemotherapy, as well as increasing success rates.

Professor Sailor explains, "The goal is to use the nanoparticles to chaperone the drug directly to the tumor, to release it into the tumor rather than other parts of the body."

The key to this nanoparticle may be its size. At 100 nm, it’s bigger than many of its cancer-fighter brethren. However, thanks to its size it can dissolve and be filtered out by the liver, spleen and kidneys with no lasting effect on them. Its size makes it able to carry more medicine and release it over a longer period of time.

Two of Professor Sailor's graduate students, Ji-Ho Park and Luo Gu, assisted on the project. Sangeeta Bhatia, bioengineering professor at MIT, and her grad student Geoffrey von Malzahn as well as Erkki Ruoslahti, another professor at the University of California, also collaborated on the project.

The project was funded by the National Cancer Institute and the National Science Foundation and its results are reported in the journal Nature Materials.

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